1. Field of the Invention
This invention relates generally to fasteners for mounting one object onto another and relates specifically to a fastener for securing lightweight insulating material to sheet metal without penetrating entirely through such sheet metal, and without welding thereto.
2. Description of the Prior Art
In the past, many driven fasteners have been provided for connecting two or more objects together in assembled relationship. Most of these fasteners have been of the nail or screw type in which the fastener penetrates a relatively thick base material such as wood and is held in place by friction. Other fasteners have been of the rivet type in which the shank of the rivet is located within aligned openings and the end is peened over to hold the objects together. Some of the prior art fasteners, particularly of the nail type, have had split legs which are adapted to spread apart on penetration and provide a clinching action to resist ready withdrawal. These fasteners obviously must be driven into a relatively thick base material in order for the legs to spread apart.
In my prior patent, U.S. Pat. No. 3,095,777, a clinch type fastener was provided for attaching insulating material to sheet metal by a clinching action and the present invention is an improvement over the same. The prior patent had a deformable penetrating end with an inwardly extending cavity having generally cylindrical walls so that when the fastener was driven the penetrating end created a bulbous portion of the sheet metal and collapsed around the same ordinarily without penetrating entirely through the sheet metal.